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Centrifugal chillers are used for cooling large buildings in a centralized air conditioning system. There are other types of chillers using screw compressors and reciprocating compressors. These are usually smaller in size. Today’s topic is about centrifugal chillers – the ultimate choice for any air conditioning installations higher than 500 RT (refrigeration tons)Basically, centrifugal chillers use centrifugal fans to move the refrigerant within the chiller circuit. As with any refrigeration circuit, there must be a compressor, a condenser, an expansion device, and the evaporator. In the case of the centrifugal chiller, the fan is the compressor. Rotating at very high speeds, it is capable of pressurizing the refrigerant gas so as to increase its temperature. Because the pressure is so dependent on the efficiency of the impeller of the compressor, the impeller is very carefully designed to match the system.The clearances between the impeller and the housing at the mouth ring (impeller suction) are made very small so as to reduce leaks back to the discharge.Usually inlet vanes that throttle the gas control the flow of the gas, and thus the chiller load. The expansion of the liquid to gas is usually made through a fixed orifice.The lubrication of the shaft bearings must be done within the chiller itself. Oil passages and shaft driven pumps (with motor driven pumps at startup) is made for lubrication.The oil will find their way to the condenser and has to be extracted back to the lubrication system. Usually there will be an eductor system to suck back the oil to the oil sump.Centrifugal chillers are usually designed for low-pressure refrigerant like R-123a.These chillers sometimes surge when running, and they are very sensitive to sudden changes in loads. Therefore modern centrifugal chillers make use of electronic microprocessors to control the various parameters and timing in order to run smoothly.Indeed, when everything is perfect, the centrifugal chiller is capable of extremely smooth operation.Folks, be cool!”Gain CONFIDENCE and ACHIEVE your life’s DREAMS!” Brian Tracy guides you through 21 Powerful Success Tips. FREE CDs.http://www.free-marine.com/link21success.htm